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NederlandsBone Spavin and Back Pain
Trauma, injury, wear and tear and conformational abnormalities can all lead to degenerative changes in horse`s joints which, in turn, progress to osteoarthritis (OA) of the affected joint.
It results when the cartilage wears through or breaks up and the underlying bone becomes exposed. This joint inflammation or arthritis is a painful process in itself, but leads to even worse changes in the joint when the body starts to react and attempts to repair itself, in what becomes a self-destructive cycle of new bone deposition and reabsorption.
The end result is chronic pain, lameness and loss of function. Not to be confused with `bog spavin`, which refers to a fluid swelling of the upper hock joint, bone spavin is an OA of the lower parts of the hock joint. The diagram (below) shows how complex this joint is, containing many small bones, each with a joint space between them, held together by small but very strong ligaments, covered in cartilage and lubricated by synovial fluid.
Diagnosis:
The commonly affected parts of the hock are the lower ones, the distal intertarsal joint and the tarsometatarsal joints. Less commonly the proximal intertarsal joint can also be affected, in which the prognosis becomes worse.
Horses of all types and ages can be affected, initial signs being lameness at the trot or, more subtly, reluctance to canter off a particular lead which improves with warming up. The farrier may identify the problem because the horse is reluctant to lift or flex the affected leg. Sometimes a hard swelling becomes visible on the front inside part of the lower hock, which is not present on the other leg.
However, horses often get bone spavin in both hocks at once, so a difference in shape of the two hocks may not be immediately obvious.
Back pain is often a secondary problem of bone spavin because the low grade but chronic lameness seen in early cases causes the horse to alter its gait and place asymmetric stresses on pelvic and back muscles. It is fairly common for a physiotherapist to get involved at this stage when the lameness is not that obvious yet to the inexperienced eye. Secondary back pain due to lameness responds well to the initial physiotherapy treatment, but symptoms (i.e. high muscle tone and muscle spasm in the back) will re-occur fairly quickly (i.e. matter of days). It is important that the physiotherapist recognises this pattern and refers the horse back to the veterinary surgeon as soon as possible. Physiotherapy treatment can be effective in reducing back pain secondary to bone spavin but only when the initial cause is treated first (OA).
The vet will initiate a series of diagnostic tests, including trotting-up in-hand on a firm flat surface, lungeing on both reins and hind limb flexion tests. When the lameness has been narrowed down to a particular leg, which is not always straight forward, especially where two or more legs are lame, nerve and joint anaesthetic blocks will be performed, to prove that the lower hock joints are the cause of the pain leading to lameness and secondary back pain. Sometimes nerve blocks, joint blocks and x-rays do not conclusively prove the existence of OA in the suspected joints, in which case scintigraphy can be used to supply additional evidence.
When bone spavin has been diagnosed and pinned down to a particular joint, a range of treatment options become available.